Zoölogy: The Science of Animal Life / Popular Science Library, Volume XII (of 16), P. F. Collier & Son Company, 1922

The immense family Colubridæ is divided into several subfamilies, the first and most extensive of which is the Colubrinæ, in which are associated all the "harmless" snakes in the world except the boas and pythons. None exceeds twelve feet long, and most of them are much smaller. Nearly all lay eggs, but some bring forth large broods of living young, among which are our water snakes, and the striped "garter" and "ribbon" snakes so numerous in our meadows and gardens. These striped snakes (Eutainia) exist in a great number of "species" or varieties most confusingly varied in coloring, some having no stripes whatever. They are very hardy, living far toward the north in Canada, and are the last to go into hibernation and the first to reappear in spring. For this winter sleep they burrow deeply into soft soil, or where rocky places exist, seek deep crevices.

The water snakes of the genus Tropidonotus follow, with many representatives in all temperate countries, one of which is the "common grass snake" of England—the only serpent in Great Britain except the viper and a rare little burrower. Ten species, with several varieties, are credited to the United States, some of which are ringed with irregular or broken bands of blackish on gray, others obscurely blotched, and some black or brown with red bellies. They are the ugliest of all our snakes both in appearance and in vicious temper; and are of no service to mankind, for their food consists entirely of fishes, frogs, toads, etc., obtained in or near the water. They live altogether in rivers, ponds and swamps; and by their dark bodies, flat heads, and keeled scales so resemble moccasins whose fierce, repellent attitudes they imitate, that in the South they are almost as much feared; hence it is well to note the differences. The harmless water snake is more slender than the deadly moccasin and may be told by the red spots on the abdomen; the undersurface of the poisonous snake is straw color, with black or gray spots on younger individuals, but has no red spots. The water snake has the plates on the underside of the tail in two rows, the moccasin in a single row. These snakes are agile swimmers and are able to spend a long time in hiding under water. They produce their young alive in broods of twenty-five to fifty, and they are as pugnacious as their elders.

Various small, ground-keeping snakes lead to another conspicuous American group, the racers and black snakes of the genera Spilotes and Zamenis, of which species and near relatives are numerous in Europe and Asia, a Malayan example growing to a length of ten or more feet—probably the longest of colubrines. Three different "black snakes" are known among us. The largest is the "gopher snake" or "indigo snake" of the sandy parts of the southeastern States, which may approach eight feet in length, and it is a variety of the still larger yellow "rat snake" or "cribo" of the tropics, which is protected about villages and houses as a good-natured exterminator of vermin. Our variety has a useful breadth of taste and lack of choler, and its haste to escape into a gopher turtle's hole when a man appears gives it one of its names, while its glossy, blue-black color, relieved only by a reddish chin and throat, accounts for the other. They are real pets, showing no fear and offering no harm; the closely related "rat snakes" of India, on the other hand, although similarly protected as ratters, are described as diabolical in temper, and thus usually remain untamable. To some extent in the South, but principally in the Northern States east of the plains, the commonest black snake is the "black racer," which west of the Mississippi, instead of being pure satiny black, with white chin and throat, appears in a bluish green hue, often with yellowish belly, and is known as "blue racer." Third, we have the less numerous and larger "pilot," whose scales are noticeably keeled and have each a touch of white. Raymond L. Ditmars takes great pains to relieve these snakes of various calumnies, as that they hunt for rattlesnakes and copperheads (whence the name "pilot"), as that they "constrict" their prey, as that they "fascinate" anything, and as that they maliciously attack human beings—on the contrary, they make frantic efforts to get away the instant their fears are aroused, and few things on earth can make better speed than this black rocket. If cornered, however, it will turn on the enemy, rear a third or more of its length, and strike repeatedly with a force and rapidity hard to avoid. Yet both the common and the indigo species quickly become docile and show signs of recognition and partiality toward their human friends. The long, slender "coachwhip snake" of the South and the equally thin and swift striped "racer" of the Pacific coast are allied species.

The genus Coluber, to which belongs the famous Æsculap snake of central Europe, is represented among us by a series of large and gayly colored species. One is the yellowish, brown-blotched fox snake of the prairie States, which is a ground keeper and a great hunter. In search of rats and mice it often haunts haystacks and barns where it should be welcome. "One snake is worth a dozen traps, for the reptile prowls into the burrows and nests of rats and mice and eats the entire brood." Similar in size (six feet) and habits is the brilliant red-and-crimson corn snake of the Southern States, which is a great mouser and also an agile climber after nests of birds, whose eggs and young it likes. Another, even larger, coluber of the South is the four-striped chicken snake, useful in its pursuit of small rodents, but, like the pilot black snake, with too great a fondness for hen's eggs and young poultry to be liked by farmers.

The big, gray, blustering "bull snakes" of the southern and western parts of the Union take their name from their habit of emitting a loud and prolonged hiss when annoyed. They keep on, and under, the ground in sandy regions, feed on small mammals and birds, and are powerful constrictors; they are also noted for morose and savage dispositions. Next to these repulsive reptiles come in classification the beautiful and gentle green snakes—slender little creatures that hunt for caterpillars and various insects through the foliage of bushes, among which their gracefully festooned length is hardly visible. South America has another group of very long and slender insect eaters and nest robbers known as "tree snakes," whose habits are similar but on a larger scale, and which have a wonderful power of riding securely on the branches, no matter how violently they are waved by the wind.

Passing over a number of small, smooth-scaled serpents, of which the pretty ringneck is an example, we come to the important genus Ophiobolus, which contains the king snakes, milk or house snakes, coral snakes and others, represented in the Old World by the genus Coronella. They vary in size from fourteen inches to six feet, and in color from gray with dark blotches to a ringed pattern of red, black, and yellow, often of brilliant beauty; but there is much individual variation.

The king snake might easily furnish material for a long chapter. Its name follows from its known disposition to pick a quarrel and fight with any serpent it meets, big or little; and quite independent of whether it is hungry, for it is as fond of eating its own kind as it is of lizards, toads, mice, birds and anything else that comes in its way on the ground, for it is not much of a climber. Our books are full of incidents of its destruction of poisonous species, and the popular belief is that it hunts for, and relentlessly pursues rattlesnakes, copperheads, etc., but the authorities assure us this is not so. If it accidentally encounters a rattler or moccasin, it kills, and perhaps eats it; but it does the same with any other serpent. It is an exceedingly quick and powerful constrictor, and careless of bites, for it is entirely immune to venom. Captive specimens have been repeatedly hypodermically injected with the poison of all sorts of American venomous serpents, as well as bitten by them, and have shown little if any effect. But wounds enrage it. Winding its lithe body round and round the doomed creature, until every part of the shining length is engaged, it tightens with such strength that the victim is benumbed, unable to bite and quickly strangled. Nevertheless these snakes submit easily to confinement and speedily grow perfectly gentle and friendly.

The common northern representative of the genus is the house snake or milk snake—names given to several other species; it is also known as "checkered adder," because of the general resemblance of its blotched form to the dreaded copperhead. It is gray above, with a series of large, chestnut-brown saddles on the back, smaller blotches alternating with them along the sides; the belly is white, marked boldly with square black blotches. The pattern and tints vary widely. This snake is a lover of warmth and a hunter of mice and rats, wild and domestic; and in search of them it frequents pastures and damp meadows, where such wild game abounds, comes much about stables and houses, and often creeps into the rural dairies that are usually close to springs. Serpents with these inquisitive habits are familiar in all parts of the world, and from time immemorial have been accused, among other iniquities, of milking cows and goats, and of drinking and spoiling milk and cream on the shelves in dairies and cellars. These beliefs survive among country people to this day, as I found out a few years ago by an extensive correspondence of inquiry, in which incredibly absurd statements were made. Of course, well-informed persons know better. The keepers of reptiles at the New York Zoölogical Park, for example, find that snakes show no liking for milk. Captive specimens cannot be induced to drink it unless suffering from great thirst. It would be a feat beyond physical possibility for a serpent the size of the largest milk snake to consume enough milk from a cow—if the reptile should be so inclined—to produce an effect noticeable to the most minute degree.

We will mention only one other sort of our harmless colubrines—the "hognose," "puffing adder," "spreading adder," as it is variously known; but the name hognose is the best. Its genus is Heterodon. Two species are common all over the eastern half of the United States and Canada, one an ugly mottled gray, the other black. They are about two feet in length, thick-bodied, with roughly keeled scales, a flat head and a pointed, upturned snout—altogether very unhandsome and forbidding-looking reptiles; and they profit by this in an attempt to frighten away whatever alarms them, while in reality themselves almost (sometimes quite) paralyzed by fear.

CORAL SNAKES, COBRAS, AND SEA SNAKES

The flattening of the head and neck practiced by the hognose as a gesture of readiness to fight, whether true or false in its implication of ability, is found among several non-poisonous colubrids elsewhere and indicates their approach in kinship to the "hooded" cobras that are the foremost representatives of the venom-bearing members of the Colubridæ. It will be recalled that we have been sketching the "harmless" section (Aglypha), and have now to take up the two remaining "dangerous" sections of the Colubridæ, the Opisthoglypha and the Proteroglypha.

The principal tooth-bearing bone in a serpent's mouth is the forward half of the upper jaw, termed the maxillary. The maxillary of each side is connected with its fellow by a small, single bone in front (the premaxillary) and otherwise is connected with the loosely connected bones of the skull by those elastic cartilages that enable the mouth to expand and take in prey of a size more than equal to the snake's head when the mouth is shut. In the serpents that do not possess a poisoning apparatus the teeth on the maxillaries are alike in size, and solid; but in the venomous kinds some of the teeth are enlarged and grooved or channeled to conduct a flow of poison into the wound made by biting. This is the case with the poison-bearing sections of the Colubridæ mentioned above, and their difference is in the relative position of the poison-conducting teeth or "fangs" on the maxillaries.

In the Opisthoglyphs these teeth are situated near the posterior end of the maxillary, and are grooved on the rear side, where they receive the poisonous fluid from a sac in the cheek. The greater number of species of this group are residents of the Old World, although we have several representatives along our Mexican border, and more southward, especially in the tropics. Most of them are little dangerous to mankind, as it is difficult for them to inflict a wound by "striking." They first seize their prey and then use their rather short fangs. The poison has a paralyzing effect, reducing the victim to helplessness. Some of these snakes must be regarded as decidedly dangerous, but fortunately all the American species may be quickly recognized by the peculiar marking on their heads, which has given the name "jew's-harp snake" to a common species of Arizona. It is believed that the vipers are an offshoot of an opisthoglyph ancestry, in spite of the forward position of their fangs.

In the Proteroglypha, on the contrary, the poisoning teeth, in all cases small, are situated near the front of the maxillaries, and they are much more dangerous reptiles, for they include the coral snakes and cobras (Elapinæ) and the sea snakes (Homalopsinæ), which are able to strike their teeth into anything they successfully attack.

The coral snakes (genus Elaps) derive their name from the broad bands of coral-red that encircle their bodies in most species, with narrow rings of black and yellow between. These brilliant colors, combined with the luster of the smooth scales, make them among the most beautiful of serpents, and a common species of our Southern States is called the harlequin. The genus is exclusively American, and nearly all belong to the tropics, where the largest become five feet long, and their bite is deadly to man. They keep to the ground, and much of the time under it, and are cannibalistic in their diet. The body is slender and cylindrical, the head small, and the eyes like beads. They are indocile, quick-tempered, and very dangerous to handle, despite the fact that they do not always resist being disturbed. Hence the widely prevalent opinion that they are harmless is a perilous delusion fostered by the fact that certain innocuous southern serpents closely mimic the coral snakes in size and colors. It should be learned and remembered, especially by visitors to winter resorts in Florida, that the poisonous ones (Elaps) have the black rings bordered on each side by the yellow ones, while in the harmless species the yellow rings are bordered by the black; also, in the coral snakes the bands of color completely encircle the body, but do not in the other kind. A very elaborate illustrated account of the coral snake and its poison apparatus, methods and serious effects, was given by Stejneger in the "Annual Report of the United States National Museum," for 1893, Part II.

The remainder of the elapine serpents (about 125 species) belong to Africa and the Orient. Typical of them are the cobras of the genus Naja, of which the species (Naja tripudians) met with from Turkestan to southern China and the Malay islands, and named by Portuguese explorers "cobra de capello" (hooded snake), is world-famous. Several species inhabit Africa and differ little from the Indian cobras, but are equally deadly. The fangs in all this group are small and are fixed in the extreme front of the upper jaw, not being erectile like the long fangs of the rattlesnakes and vipers. Cobras vary much in coloration, and Mr. Scully reports that he has killed South African specimens of light yellow, jet black and all intermediate hues.

The cobra is a fierce fighter and, when reared up, with expanded hood, looks very formidable. Anterior to the head the ribs lengthen and then gradually shorten to normal dimensions. These lengthened ribs, about twenty in number, lie, when the snake is quiescent, more or less laterally along the spine. But when the snake becomes excited, the neck bends and the ribs spring out at right angles. Over them the loose folds of skin expand umbrella fashion. When much enraged, the cobra spits drops of venom at its enemy. These are propelled a distance of about four feet.

The cobra is found all over South Africa, but is especially plentiful in the dry, sandy deserts northwest of the Cape. There extensive colonies of large mice abound, patches of ground being thickly honeycombed with burrows. In these the cobras dwell—apparently, as in the case of the puff adders, on the best of terms with their hosts, upon whom they principally feed, reminding one of the tenancy by the Western rattlesnake of prairie-dog "towns."

A close relative of the cobra is the ringhals (i. e., ringneck), known as the "spitting snake," the explanation of which Mr. Scully furnishes from personal experience thus:

"The ringhals, when excited, exudes a quantity of venom, which drips down the fangs and lodges behind the abrupt, horny, lower lip. Upon this the angry snake directs a blast of air through its extensible windpipe, with the effect that a jet of fine venom spray is emitted toward an enemy. This jet may reach a height of six feet. That the eyes are aimed at I have proved by experiment. If the poison reaches them blindness, which may be permanent, results. The bite of the ringhals is highly venomous, but the snake appears to prefer disabling its enemy by means of the spray of venom."

The most novel and interesting of Mr. Scully's contributions to African herpetology, however, is his story of the mamba (Dendraspis angusticeps), which he calls "the head of the family." It is the longest venomous snake in the world, probably running to fifteen feet in exceptional cases, but is slender and primarily a tree snake. This naturalist declares it to be the most dangerous of all snakes, as it is highly aggressive at times and its speed is quite extraordinary. If disturbed during the pairing season, the mamba attacks without hesitation; and if at any time one happens to get between the mamba and its dwelling, the snake rushes straight for its objective and, in passing, strikes swift as lightning at the intruder. It progresses in a series of bounds, suggestive of the successive uncoilings of a steel spring. There are two varieties, one colored a vivid grass-green, the other steely black, both so dreaded that the news that a large mamba has been seen will cause the vicinity to be shunned—perhaps for months.

"The mamba has the habit of lying coiled among the branches adjacent to a footpath in a forest. Woe to the passing wayfarer in such a case! If he touch a twig, and thus impart the least tremor to the snake's lair, a lightning-swift stroke upon face, neck, or arm seals his doom. Such a stroke may be delivered either forward or sideways, with equal speed and effectiveness."

The most feared of the cobra tribe in India and eastward is the king cobra, or hamadryad, which often exceeds a dozen feet in length and is "the largest, boldest and most dangerous of all venomous snakes," in Boulenger's opinion, "for when disturbed it does not content itself with merely sitting up and expanding its hood, but will almost invariably attack." Fortunately it is not numerous anywhere in its range from the Himalayas to the Far East; and it is useful in that it feeds exclusively on snakes, small pythons, kraits, rat snakes, and the common cobra. Its bite will kill a man in an hour or two; and it is recorded that an elephant bitten by one died in three hours.

Nearly all the serpents of Australia belong to Elapinæ, and are exceedingly dangerous. Among them are the "black snakes," the females of which are called "brown adders"; the "tiger," so called from its colors; and most dreaded of all, the "death adder," which is distinguished by a peculiar tail end, and by the fact that the head is made distinct from the body by a narrow neck, giving it a viperlike appearance. When disturbed it flattens out the whole body.

A few words about the sea snakes will close our account of the poison-bearing colubrids. These are set apart in the subfamily Homalopsinæ, on account of the structure of the tail, which is flattened vertically into a combination of swimming organ and rudder, for they live in the estuaries of Oriental rivers, and go far out to sea in their search for food; and are to be met with from the Persian Gulf to Polynesia and Japan. All are very poisonous, feed mainly on fishes and produce living young; and all are clothed in varied and brilliant colors. Living in the sea, or in tidal inlets, their movements in the clear blue water are agile and elegant; and in the Bay of Bengal they are sometimes seen congregating in large shoals.

We turn now to the last and most advanced family of serpents, the vipers, rattlesnakes, moccasins, copperheads, and so forth (Viperidæ).

VIPERS, MOCCASINS AND RATTLESNAKES

"Viper" is an old French-Latin word, meaning "bearing living young," which was noted as distinctive from the egg-laying habit of other snakes, and peculiar to the single species that the people of southern Europe knew—the small Vipera verus, or asp, from which the large and widespread family derives its name. The vipers differ from the colubrids in important particulars. Their bodies are thick in proportion to their length, which rarely exceeds six feet, and this and their weight make them unable to run rapidly or (with one exception) to climb trees. The sturdy body narrows into a slender neck supporting a distinct head, given a flattened, triangular form by the expansion of the hind head on each side to accommodate the great poison sacs with which these snakes are provided. The maxillary is a stout bone in the fore part of the upper jaw, and carries on each side a long, backward-curved fang, which is tubular and is connected at its root with the extremity of a duct from the poison sac. When the serpent's mouth is closed, or it is swallowing anything, these fangs, which in a large snake may be an inch and a half long, lie back in a fold of the flesh out of the way; but when the mouth is widely opened they spring forward, and when the head is darted forward to strike a prey or an enemy, they are driven down into its flesh and the venom spurts through them into the wound, with benumbing and deadly effect. They are frequently broken or dragged out, and then new ones arise from behind to replace them. The eye is large, dull, and catlike in its pupil; the scales are strongly keeled and dull in hue in the desert dwellers, but often gay with colors in intricate patterns in the forest dwellers; and the short and stumpy tail may end in "rattles," or a horny tip, or neither. Nearly all give birth to large broods, which are as vicious at birth as are their mothers. The family has two sections, marked by the absence in the first, and the presence in the second section, of a deep pit in the broad scale on the head between the nostril and the eye.

The original little "viper" of Europe and Asia is more a nuisance than a peril, for it is rarely more than a foot long, and its bite would be fatal only to a small child. A larger species, the sand viper, ranges from Italy to Armenia. India, Burma and Siam, however, have a member of this group which is pronounced by Sir J. Fayrer as next to the cobra the most dangerous serpent of the East—the daboia, or Russell's viper. It is nocturnal, not aggressive, and makes a loud hissing when anyone comes near it, so that it does not cause as many human deaths as it might; but frequently kills grazing cattle by biting them on the nose. The greatest and worst of these snakes belong to Africa, where the northern deserts are infested with two greatly dreaded species—the horned and the saw vipers. The former has two sharp hornlike protuberances above the eyes, and Canon Tristram writes that its usual habit is to coil itself on the sand, where it basks in the impress of a camel's footmark, and thence suddenly to dart out on any passing animal. Horses as well as men are in constant terror of it, for it will attack without any provocation.

The worst of the African vipers, nevertheless, is the puff adder, which ranges over the whole continent, and may grow to a length of six feet, with a girth equal to a man's thigh.

"The coloration of the puff adder," Mr. Scully writes, "is in groundwork a series of delicate browns, with more or less regular curved transverse patches darkening to black and edged with vivid yellow. Its scales are keeled; its short tail tapers suddenly to a point. It is a sluggish creature, incapable of swift progression. When disturbed, it flattens itself to the ground, the air expressed in the process causing the warning hiss which has saved many a life. But if the foot of the intruder touch it, or even tread in its immediate vicinity, the puff adder lunges either forward or sideways, with a swiftness that the human eye cannot follow, and, having buried its fangs deep in the flesh, holds on like a bulldog, forcing two streams of venom into the tissues. The expression of this snake—its square muzzle and glaring, lidless eyes with vertical pupils—the extraordinary gape of the jaws and the huge, erected fangs, form what is probably one of the most fiendishly menacing combinations in nature. Nevertheless, apart from its head, the puff adder is a creature of great beauty. The 'night adder' (Causus rhombeatus) is much dreaded on account of its habit of lying at night in pathways and failing to move out of one's way. This snake is one of the exceptions to the rule of the viper class, in that it is not viviparous. It has another remarkable peculiarity: the poison glands, instead of lying compactly embedded in the maxillary muscles above the angle of the jaw, are much elongated, and lie one on each side of the spine."

All the pit vipers are American except a few species in southern Asia, some of which are arboreal in habit and have red prehensile tails. Our American species fall into two genera: Ancistrodon, the moccasins (no rattles), and Crotalus, the rattlesnakes.

The "upland moccasin" of the South is the "pilot" or "copperhead" of the North, where it still exists in forested and rocky districts from Connecticut and the Great Lakes to Texas, and is particularly abundant in the rough hills beside the Hudson River, and thence southward along the Alleghenies. Its general hue is yellowish brown, becoming chestnut or coppery red on the head and end of the tail, which terminates in a hard point. Along the back, meeting irregularly on the midline, are chestnut-hued blotches that divide on the sides, forming inverted Y's; the belly is yellowish with distinct black blotches, leaving the throat clear. After one has seen a copperhead he is not likely to confuse it with the milk snake or any other. Its haunts and habits are much the same as those of the eastern rattlesnakes, nor do I consider it any more aggressive in spite of a rather over-blackened reputation, nor so deadly in the effects of its weaker venom. It is bad enough, however, and should be killed on sight wherever children or pet dogs are likely to meet with it. This upland moccasin is named in science Ancistrodon contortrix; its brother species, the water moccasin, is A. piscivorus.

The moccasin is a larger, heavier snake than the copperhead, and a dweller in the sluggish rivers and swamps of the Gulf States and northward to North Carolina and Kentucky. The moccasins commonly lie on the branches of bushes at the edge of the water; and if escape from danger be possible they quickly drop into the water and swim away beneath it to some hiding place. If suddenly surprised they coil and open the mouth widely toward the intruder, showing its white interior that has given them the name "cotton mouth" among the darkies, who fear them greatly, especially as they work in the rice fields. Mexico has a similar species.

Closely allied to the copperhead and moccasins are two very dreadful snakes of the American tropics—the "fer-de-lance" of the French islands of the West Indies, and the "bushmaster" of Brazil. The former reaches a length of six feet, and the bushmaster, or surukuku, as the Indians name it, to twice that length, thus rivaling the great viper of India. Both have all the ferocity and power of their race exaggerated to the limit, and hundreds of human lives are sacrificed to them every year. Every traveler has thrilling tales about them. Leo Miller, a cool-headed man of science, takes very seriously the fear this creature inspires. He reminds us that a bushmaster ten feet long has fangs an inch and a half long, and injects nearly a tablespoonful of poison at a single thrust. A man would survive such a dose but a few minutes. When once a bushmaster fell from a tree branch into his canoe everybody in it sprang overboard, and some narrowly escaped drowning. Such deadly creatures would make the tropical world unendurable were it not that most of the time they are sluggish and peaceful; but a little fright, or a protective instinct in regard to their eggs, sets them off with the suddenness of a released spring.

In taking up the rattlesnakes we have a sure guide in Dr. Leonhard Stejneger's "Report," describing all the species of North America (the group Crotalinæ is confined to this continent, Central America, and a single species in South America). The special peculiarity of the group is the queer "rattle" (crotalus) at the end of the tail. This consists of a series of loosely connected, somewhat cone-shaped, horny capsules, each of which originally covered the terminal vertebra of the tail. On sloughing the skin this covering remains, but is soon pushed away by the new capsule formed beneath, and partly within it, which in turn is pushed out and replaced by a third, and so on, until sometimes a dozen remain linked together; and when the serpent vibrates its tail, as most snakes do when excited, they rattle against one another, the tone of the "music" rising as the excitement, and speed of vibration, increases. The sloughing is irregular as to frequency, however, especially in young individuals, and may not always produce an addition to the rattle, and the appendage itself may be broken, so that the number of pieces, or buttons, in the rattle is not a trustworthy measure of the age of the snake.

The smallest of the crotalids are the ground rattlers (genus Sistrurus), of which we have two species, and there is one in Mexico. The northern kind, widely known by its Indian name "massasauga," ranges from eastern Pennsylvania and Ontario to northern Minnesota and Kansas, and thence to Texas. The Southern States have a second species commonly called "ground rattler." Both are grayish brown with chestnut or darker dorsal blotches, and are inhabitants of the prairies, with their swamps and marshes. The largest do not exceed forty inches, and their bite is correspondingly weak in effect.

The remainder of the rattlesnakes belong to the genus Crotalus.

The commonly seen species of the region east of the dry plains was named Crotalus horridus by Linnæus, and this is one of the few instances in which his name has defied change by the systemists. It formerly was to be found as far east as central Massachusetts, but there, as elsewhere, civilization has killed it off, so that now it survives only in the Appalachian glens, and in thinly settled tracts farther west and south. Its general color above is yellow-brown, below nearly white; and the body is banded with blackish, the bands taking a zigzag form behind the neck, and the tail is black. It rarely exceeds a yard in length, and is, as a rule, timid and nonaggressive; but a good deal remains to be learned about its habits and breeding.

Far more formidable than this is the diamond-back (C. adamanteus) of the low, coastal region from North Carolina to the lower Mississippi River and throughout Florida, where it is far more common than is desirable. This rattler may exceed eight feet in length, and has corresponding power of harm. It is partial to the neighborhood of water, where its ground-running prey is most numerous; hence it is frequently spoken of as the "water rattlesnake," to distinguish it from the banded species, or "timber rattlesnake" of the same region, which is more habituated to forested districts, with rocks. A race of C. horridus, usually large and vicious, exists in the coast swamps, and is locally called the "canebrake rattler." The diamond back itself takes its name from the lozenge-shaped patches of dark color formed on its upper surface by the crossing of diagonal narrow bands of bright yellow on a greenish gray ground. The literature relating to this terrifying snake would fill hundreds of pages. Raymond L. Ditmars of the New York Zoölogical Park, gives this description:

"Most deadly of the North American poisonous snakes, and ranking in size with the largest of the tropical venomous serpents of both the New and the Old World, this huge rattlesnake, with its brilliant and symmetrical markings, is a beautiful and terrible creature. Ever bold and alert, ever retaining its wild nature when captive, there is a certain awe-inspiring grandeur about the coil of this formidable brute; the glittering black eyes, the slowly waving tongue, and the incessant, rasping note of the rattle.... The mere vibration of a step throws the creature upon guard. Taking a deep inhalation, the snake inflates the rough, scaly body, to the tune of a low, rushing sound of air. Shifting the coils to uncover the rattle, this is 'sprung' with the abruptness of an electric bell. There is no hysterical striking, but careful watching, and if the opportunity to effect a blow with the long fangs is presented, the result is generally mortal."

A large and very showy western analogue of the diamond-back, known by the sinister specific name atrox, occurs from central Texas to California. One of its varieties is red, with darker red markings and a white tail. The familiar rattlesnake of the plains east of the Rocky Mountains is Crotalus confluentus, which is of moderate size and dull hue; its mainstay of food is found among the prairie-dog towns. A similar but smaller species (C. oregonus) takes its place west of the Rockies, from British Columbia to southern California. The "tiger" rattlesnake, yellow barred with black; the "horned" rattler, which, like the Egyptian horned viper, has a trick of advancing sidewise, and consequently has the popular name "sidewinder"; and the slender green rattlesnake, are small species of the deserts along the Mexican border.

CHAPTER XXII
BIRDS—KINGS OF THE AIR

A bird is an animal clothed with feathers and having the forelimbs adapted to flight.

The birds constitute a class in the phylum Chordata, and otherwise are combined, in the group Sauropsida, with the Reptilia, with which they agree more closely in anatomy than with any other group, one prominent particular being that both have a single condyle, in contrast with the mammals and amphibians where the condyle is double. In fact primitive reptiles—probably of the stock of dinosaurs—are the ancestors of birds, the divergence having occurred probably in Carboniferous time. Of the earliest divergent forms, the rocks have as yet yielded no specimens, the most ancient bird forms recovered showing a degree of development in the new type that must have been preceded by a long history of evolution from its reptilian source.

The oldest fossil bird known is that named archæopteryx, whose remains are found in the Jurassic slates of Bavaria, which represent the beginning of the Mesozoic or Age of Reptiles. In much of its anatomy, and in the possession of perfect feathers, it is a true bird, yet it retains many reptilian features. Its body was about the size of a small crow; its legs were rather long, with well-developed feet of four toes suitable to grasping a perch; its wings were short and probably feeble, for the shoulder girdle and ribs are weak and the sternum is rudimentary. It is plain that it was arboreal in habits, but a poor flyer, and was aided in scrambling about the branches of trees on whose leaves and bark it may have fed, by the fact that three digits of the rather lizardlike wing hand terminated in strong claws, while the thumb was entirely free.

The practical value of this clawed hand is illustrated in a living bird—the hoatzin, of northern South America—which exhibits in several ways the probable appearance and manners of the archæopteryx. "It haunts the sides of lagoons and rivers where a thick growth of low trees projects over the stream or the mud left bare by the tide. When disturbed the bird flies off awkwardly with a violent flapping motion, or leaps from bough to bough, erecting its crest and expanding its wings and tail. The note is sharp and shrill, and has been described as a hissing screech. The food consists of leaves and fruit. The conspicuous nest, placed on low trees or shrubs, is a loose platform of spiny sticks and twigs with a softer lining, and contains from three to five yellowish eggs, spotted with reddish brown and lilac. The young, which can see and run as soon as they are hatched, have a claw on both forefinger and thumb, by means of which they creep about the thickets, and hook themselves over the branches, assisted by the bill and feet. They can also swim and dive."

The most striking features of the archæopteryx were its head and tail. The skull is fairly avine, and the rather short and blunt bill was furnished with conical teeth, nearly equal in size, and set in a marginal row in distinct sockets. Still more lizardlike was the tail—a prolongation of the backbone nearly as long as the body, along each side of which sprouted strong feathers forming a horizontally flat tail with a rounded end.

The next that we know of bird evolution is derived from the discovery of the fossil remains of toothed birds in the Upper Cretaceous formations of Kansas—that is, in the more recent half of the Mesozoic Age. They differ greatly not only from archæopteryx but from each other, and are represented by several species. One type (Hesperornis) was a wingless, diving bird of great size, whose long, heronlike beak was studded with small, sharp teeth, all alike, implanted in a continuous groove; its legs were so hinged to the compressed pelvis that they could be extended almost level with the back, and the lobed toes thus became lateral winglike paddles of great power. The other type, represented by Ichthyornis and its relatives, also had a long, stout bill set with teeth, but each in a separate socket. Ichthyornis was about the size of a pigeon, and its strongly developed wing bones and deeply keeled sternum show that it was a bird of powerful flight, and apparently gull-like habits. So far as we know neither of these Cretaceous birds had any progeny. When, after an immensely long period, other fossils come to light in rocks of the middle Tertiary period they bear few traces of ancestry, and exhibit little relation to the great mass of modern orders. They are the "flightless birds," possessing no wings but running about on massive legs; and the group includes the extinct æpyornis, dinornis, and moa, and the existing ostriches, rheas, emus, cassowaries, and kiwis. Some ornithologists question whether this "ratite" group, characterized by having no "keel" on the sternum, did not have an origin and line of descent quite distinct from those of both the Cretaceous toothed birds and the modern "carinate" type which possess a medial crest or "keel" on the breastbone for the support of the flight muscles; but the more general opinion is that they are a variant from very early birds with wings.

HOW A BIRD IS BUILT

Since its feathers are the one thing that marks a bird, outwardly, as different from other classes of animals, we ought first of all to learn what feathers are, and what purpose they serve. A quill feather, such as may be picked up in any farmyard, has a horny, hollow stem or "shaft," which is bare at the closed large end or "base," but has two soft, winglike expansions toward its tapering end that together make its "vane." This thin, flat vane consists of delicate branches, "barbs," studded with tiny hooks, the "barbules," holding each adjacent branchlet in place, but letting the whole vane bend and spring. The whole beautiful thing is really very strong and elastic, as it must be to push as hard against the air as a bird's wing has to do. The vanes vary much in shape, and in the degree to which the branchlets are disconnected into a fluffy looseness. Ostrich plumes, and those of the birds of paradise, owe their beauty to the fact that each branch in the vane is loose, and bears little disconnected branches of its own; and in many feathers no vane at all grows, so that they resemble hairs, when fine, and bristles when coarse, as is seen about the mouth of the whippoorwill and some flycatchers. The nestling plumage or "down" is of this character. The lovely plumes of egrets are slender stems of feathers having in place of a vane scattered soft hairs. In some sea birds the feathers are so stiff and hard as to be almost like scales. Those of water birds, and especially the divers, are wonderfully close, thick, and greasy, so that the down that forms an undercoat for warmth, and the skin beneath it, never gets wet.

Feathers, then, serve their wearers first of all as clothing—very thick and warm in birds of cold places; and doubtless this beneficial modification of the primitive reptilian scale, by reason of its conserving the warmth of the body, and gradually increasing the temperature of the blood, has been largely instrumental in enabling birds to rise so far above the grade of their cold-blooded and sluggish ancestors.

Most animals whose lives are spent in the open air and light show more or less color in their coat, but none are more beautifully adorned than birds. The most brilliant examples are to be found in the tropics, and some of the gayest in our colder land, such as the tanagers and humming birds, are strays from large tropical families noted for gaudy attire.

The color we see in plumage may be due to either of two conditions. It may, as is usually the case, be simply coloring matter deposited in the substance of the feathers. But where the plumage gleams with changing rainbow lights, as on the fiery throat patch of the humming bird, on the neck of a dove or on the purple-black coat of the grackle (crow blackbird), these splendid reflections are caused by very minute wrinkles on the feathers, that break up the light. It is the same effect, called "iridescence," as is seen on the mother-of-pearl and on a soap bubble. Blue is usually an effect produced by certain coloring matter not blue underlying a thin covering of feather substance; and when you pound a blue feather into dust that dust will be black or gray—or, at any rate, not blue. Birds of the same group are colored much alike, as a rule.

In some cases the style of colors worn appears to be the best for the safety of the birds of the group by making them hard to see as long as they keep still. Thus most birds whose lives are passed on or near the ground, and which build their nests there, are dull in coloring; they are in danger from more enemies than are tree-dwelling birds, and must be able to hide better. No bird of nocturnal habits is brightly colored. It is mostly among the small, quick-flying species, such as warblers and finches, that we find the gayly dressed ones. They are birds of the sunshine, and usually migratory. In most cases when birds have a plain dress there is little difference in it between the male and the female; but whenever you find a species of bird wearing a gay, ornamental dress, it is almost always the male that sports these fine feathers, while the female and young are clothed in dull yellow, drab or brownish tints. This appears to be another measure of safety. The males can wander about, look out for themselves, and take to flight when danger threatens; but their mates must sit quietly on their nests, and trust for safety for themselves and (what is really more important) their eggs or young mainly to not being seen. In their plain colors they blend into the foliage and the shadows amid which they sit, and so are more likely to escape the sight of prowling foes.

Feathers are not intended to remain permanently; they become worn and faded, or are lost, so that at regular intervals the bird needs a new suit of clothes. Twice a year, therefore, in spring and autumn, they are pushed out by new ones sprouting in the same feather-growing pits. This shedding of the feathers is called "molting," and it is analogous to the shedding of the outer, horny pellicle of its skin by a snake or lizard. Their molting is not very noticeable in land birds, because the feathers drop out little by little; otherwise the poor creatures would be left quite naked, and unable to fly. In most birds the new feathers that come in are the same in pattern and color as those they displace, so that the new plumage differs little if any from season to season; but some birds acquire a new coat for winter that is decidedly different, and sometimes snowy white, making them inconspicuous amid the snow.

The largest and most important feathers in a bird's outfit are those of the wings and tail, by means of which it flies and controls its progress. How birds are able to keep themselves aloft in the air, and move through it at will, is not yet understood. That it requires great strength of wing muscles, and rigid support for them is evident. Therefore we find the head of the arm bone (humerus) fastened by stout ligaments to a great shoulder blade sunk in the flesh beside the fore part of the spine, and also braced in two directions by other interior bones, one of which extends down to join its opposite fellow at the front end of the breast bone, and form the "wishbone" (the united coracoids). This solid bracing by bones and tying by ligaments gives the needed firmness to the wings; and enables their powerful muscles to work them.

How great these muscles are you will know when I tell you that the thick mass of "white meat" in the breast of the fowl carved at your table consists only of the two principal muscles that move the wings when a downward stroke is made. They, in their turn, are attached at the base to the broad surface of the breastbone, or "sternum" and its projecting keel. Beyond the wrist joint stretches a large, misshapen hand, which consists mostly of one great forefinger, in the tough flesh of which the big quills, or outer flight feathers, called "primaries," are rooted. Lying over their bases, when the wing is folded, is a row of somewhat smaller quill feathers called "secondaries." Above those are the small and close "wing coverts."

The tail is very important in guiding and checking a bird in flight, and is useful in various other ways, and may also be extremely ornamental. The tail quills are always in pairs, making an even number of feathers. This results from the reduction to a mere stub of the long clumsy tail worn by the archæopteryx and its fellows. The quills continued to grow in pairs out of the side of the tail as it diminished until all that there is room for (ten or twelve pairs) are now rooted side by side around the edge of the condensed coccygeal bones.

Birds are, as a class, the most active of animals, and their temperature is highest; this means a large consumption of oxygen, and the windpipe is usually capacious, yet the lungs are not large, but are supplemented by another apparatus for aeration. Opening out of the lungs are several pairs of air sacs, amplest in those birds that are much on the wing, which not only occupy spaces between the muscles and organs within the chest, but in many cases extend into the neck and head, and even into the limb bones, which in most birds are hollow.